Conventional magnetic resonance imaging has spatial imaging resolution of about 1 μm. Motivated by the potential of combining 3D imaging capability of conventional magnetic resonance and the atomic resolution of scanning probe techniques that utilize mechanical cantilevers, a new atomic resolution 3D magnetic resonance imaging technique was introduced. This method, magnetic resonance force microscopy (MRFM), uses a microscopic magnetic particle as a source of atomic scale imaging gradient fields and a mechanical resonator as a sensitive detector of magnetic resonance, as opposed to more conventional inductive techniques. Proof-of-concept demonstrations of MRFM were carried out for various magnetic resonance systems including electron spin resonance, nuclear magnetic resonance, and ferromagnetic resonance.
However, while MRFM is rapidly progressing by the incorporation of smaller magnetic particles and more sensitive mechanical resonators, current MRFM imaging resolution of ˜1 μm remains at the level of conventional MRI inductive detection. A single nuclear or electron spin has not been successfully detected yet due to significant technical challenges.
Additionally, while achieving single spin sensitivity and resolution in a 3D imaging technique is of great significance, the MRFM technique also places challenging demands on the technical requirements, such as operation at very low temperatures, miniaturization of mechanical cantilevers, and the integration of magnetic nanoparticles into resonating structures.